Rails: Avoiding duplication errors in Factory Girl…am I doing it wrong?

Question

Suppose I have a model user, which has a uniqueness constraint on the email field

If I call Factory(:user) once all is well, but i

Answer 1

Here's what I do to force the 'n' in my factory girl sequence to be the same as that object's id, and thereby avoid collisions:

First, I define a method that finds what the next id should be in app/models/user.rb:

def self.next_id
  self.last.nil? ? 1 : self.last.id + 1
end 

Then I call User.next_id from spec/factories.rb to start the sequence:

factory :user do
  association(:demo)
  association(:location)
  password  "password"
  sequence(:email, User.next_id) {|n| "darth_#{n}@sunni.ru" }
end